NAVIEN NHW700-180SE-NG

This site calculated the 209 therms figure; the registry does not list it. The calculation combines the registry's UEF, the ratio of hot water delivered to energy used, with the DOE test's daily hot-water draw. For this model the UEF is 0.81, taken from DOE CCD data retrieved 2026-09-19. The comparison class is the 397 models registered as a gas tankless unit at the high draw pattern. This model ranks 323rd lowest energy use of 397. That places it in the highest quarter of its class for energy use. The figure holds only at the test's daily draw, and annual use at other draw levels is not available here. The steps are set out in how this site calculates annual energy and cost.

The high draw pattern stands for a larger household, or one where showers and laundry overlap. This model's maximum flow rate in gallons per minute is 4.7, as listed in the registry. The data here does not say how many fixtures that flow can supply at once. For a household that uses hot water at the high pattern, 209 therms is the figure that applies. A reader who wants lower gas use at the same draw pattern should know that half of the 397 models use 182 therms or less. You can list models in the same class by searching for a same-class replacement by model number. For a smaller household, this high-pattern figure may not match its use.

This text does not give a running cost for 209 therms a year. The cost depends on your state's average residential gas price, so the page calculates it from your ZIP. The cost calculator on your own ZIP applies that rate to this model's annual figure. The same rate applies to the 27 therms gap above the 182 therms class median. So the cost of that gap also depends on your state. The installed price range appears in a separate block on this page, with its source and date. That range is a modeled installed cost, not a quote, and this text does not restate its figures.